In Patent Literature 1, “braking force distribution control in which distribution of a braking force is changed in response to a request for braking performance under a high braking load without enlarging a braking device of a vehicle” is described. More specifically, it is described that “determination means for determining whether a high braking load state is established on the basis of intervals and the number of executions of braking execution processing and distribution control means for changing front and rear wheel braking force distribution of the vehicle when it is determined that the high braking load state is established are provided, the high braking load state is detected in the cases where the braking execution processing of requesting the braking force that exceeds a specified braking force and driving execution processing of requesting a driving force that exceeds a specified driving force are alternately executed and where the braking execution processing is executed for the number of times that exceeds the specified number of times at a shorter braking execution interval than a specified period of time, and the front and rear wheel braking force distribution is changed by decreasing the braking force on front wheels and increasing the braking force on rear wheels”.
The brake control device described in the Patent Literature 1 is based on the following idea; “it is considered that the braking device on the rear wheel side has room for heat capacity when compared to that on the front wheel side. Accordingly, in the case where the braking load is higher than that in normal use environment, the braking force distribution control is temporarily executed such that the rear-wheel braking device compensates for shortage of braking capacity or the braking performance of the front-wheel braking device. In this way, the braking performance or the braking capacity that is requested under the high braking load can be realized without enlarging the braking devices”. Accordingly, the brake control device in the Patent Literature 1 specifically controls such that “when it is determined that the braking load is increased due to a travel pattern in which rapid acceleration and rapid deceleration are repeated, the front and rear wheel braking force distribution is initially changed to be biased toward the rear-wheel side in order to decrease the braking load of the front-wheel braking device that is actuated to generate the relatively large braking force and to prevent the front-wheel braking device from being brought into an overheated state, and, when a decrease of the braking load by such a change in the distribution is insufficient, a gear stage of a transmission is thereafter lowered, so as to suppress an increase of the load of the braking device”.
In regard to the brake control device, from a perspective of heating, it is necessary to consider not only the travel pattern in which the rapid acceleration and the rapid deceleration are repeated but also situations where various braking operations are performed. That is, of the various braking operation situations, there is a situation where requested performance for the front-wheel and rear-wheel braking devices contradict each other. More specifically, there is a case where the large braking force is generated in a short period of time by rapid braking from high-speed travel, and there is a case where the relatively small braking force is generated over a long period of time on a downhill road or the like. In the short intense braking operation, the relatively high heat capacity is requested for the front-wheel braking device. Meanwhile, in the long mild braking operation, the relatively high heat capacity is requested for the rear-wheel braking device. The heat capacity of the braking device can be increased by thickening a brake disc, enlarging a brake caliper, and the like. However, any of such changes is not preferred from a perspective of reductions in size and weight of the device.